The present invention relates to a cutting tool and more particularly to a cutting tool specifically adapted to cut the welds holding nozzles in the wall of a governor chest and, after removal of the nozzles, refinishing the nozzle seating surfaces of the wall.
A governor chest finds use as a speed control device in steam driven turbines. Typically, a governor chest has an inlet for steam, a valving chamber, a removably affixed top cover, and a plurality of outlet nozzles welded in openings in the bottom wall of the chest and extending upwardly from the interior surface of the bottom wall. A control mechanism extending through the top cover operates a mechanism within the chest to in turn operate a plurality of valves. The valves selectively block the nozzles and are operated in a preselected sequence to permit more or less steam to pass through the nozzles to the turbine.
The nozzles in the governor chest must frequently be replaced because of corrosion, wear, and the cutting action of high pressure steam. At the present time, the usual process of removing a nozzle requires the use of hand-held and make-shift cutting tools for cutting away the weld material which holds the nozzle in the bottom wall of the chest. Experience has shown that it is difficult to cut away the weld material utilizing present methods. The tool "chatters" or jumps about as the cutter tool bit rapidly and repeatedly strikes the weld material. The chatter makes it difficult to hold the tool in its proper position and as a result it frequently damages the surface on which the nozzle is seated. When the seating surface is damaged, it frequently requires that the entire governor chest be removed for repair or replacement, a very expensive and time-consuming operation. Also, once the weld material has been cut away and the nozzle extracted from the wall of the chest, the turbine casing containing the nozzle block has to be removed to the machine shop for remachining if the nozzle seating surfaces are damaged.